1. Field of the Invention
The present invention generally relates to an atomizer burner for a motor vehicle heater. In particular, the present invention relates to such an atomizer burner having a baffle plate.
2. Description of the Related Art
Atomizer burners with which the energy bound in fossil fuels can be converted into heat energy are already in use in the various fields as exemplified by the International PCT document WO 87/00605 or the published German Patent Application DE 39 01 126 A1. In the area of motor vehicle heaters, atomizer burners or nozzle atomizer burners in the power range of less than ( less than ) 10 kW are generally not used, since the atomization quality is not considered sufficient at smaller powers and a high electric power consumption is necessary to achieve adequate atomization quality. In addition, atomizer burners exhibit poor combustion characteristics in the partial load range since in such load range, the atomization quality is poorer than under a full load.
Finally, nozzle atomizer burners of the known type exhibit poor cold starting behavior, because based on the viscosity of the fuel which increases as the temperature decreases, the atomization quality is adversely affected. Here, large fuel droplets pass unvaporized or only partially vaporized through the combustion chamber part thus causing high starting emissions. A poor exhaust gas quality, if only during the starting phase, cannot be tolerated nowadays with consideration of the increased sensitivity of the market with respect to environmental issues.
Thus, in view of the above, the primary object of the present invention is to provide an atomizer burner for a motor vehicle heater which, even at lower powers in the partial load range and during the cold start phase, still provides good combustion behavior and low emissions.
This object and other advantages are achieved by the embodiments of the present invention described below.
In accordance with one embodiment of the present invention, an atomizer burner for a motor vehicle heater is provided with a combustion chamber part which contains a baffle barrier, and with an atomizer which atomizes the fuel into the combustion chamber part. Baffle plate which acts as a baffle barrier is provided at a distance from the atomization point of the atomizer which is smaller than the diameter of the combustion chamber part or the diameter of a cylindrical heat shield which extends in the combustion chamber part. The baffle plate which acts as the baffle barrier has the effect of flame stabilization which acts advantageously to reduce flame noise and the improve combustion, especially at smaller powers or in the partial load range of the burner. The baffle plate is especially advantageous in the implementation of compact combustion chambers for liquid fuels. The burner equipped with the baffle plate can process even poorer atomization qualities by the plate without this adversely affecting the combustion behavior. Therefore, the present invention allows improved implementation of partial load stages in which the atomization quality is poorer than in the full load stage.
The baffle plate can be conical, convex, or concave shaped, among other shapes. The arrangement of the baffle plate in the flame zone facilitates re-ignition of the fuel on the glowing disk after flame blow-off, which may be caused, for example, by air bubbles in the fuel line. In addition, CO and HC emissions can be reduced when the combustion process ends by the fuel reacting on the glowing baffle plate.
The baffle plate can be made as a disk with a collar with a height of 2 mm for instance, which extends against the atomization direction of the fuel so that it forms a cup shape which is open to the atomizer. The ratio of the baffle plate diameter to the fuel chamber diameter is preferably between 0.6 and 0.9, and the ratio of the axial distance of the baffle plate from the atomization point to the combustion chamber part diameter is preferably between 0.3 and 0.6. Suitable dimensioning of the baffle plate, compared to the other aerodynamic measures, yields only a slightly increased pressure loss in the combustion chamber part. For example, the tangential component of a combustion air flow which is delivered with a swirl is only insignificantly disrupted, so that the combustion gases can also flow downstream of the baffle plate still having a swirl component. The baffle plate is preferably fixed with mounting clips.
In one embodiment, the baffle plate can have openings in the form of slots and/or holes, the openings being made preferably in the form of defined perforation of the baffle plate. However, the baffle plate can also be made as a ring with a central through hole.
Furthermore, in one especially preferred embodiment, a chamber is provided on the baffle plate into which a glow means in the form of a glow pin, for example, of ceramic, or in the form of a glow plug, projects. By providing such an arrangement of the glow means in the area of the restricted flow upstream of the baffle plate, the starting behavior of the burner is thereby improved. The chamber is preferably made such that the glow means projects into it so that the radiant energy of the glow means can be used downstream of the atomization device to heat the components of the baffle plate. In this way, the starting characteristics of one such burner is greatly improved.
The baffle plate can, among others, be fixed on the combustion chamber part, on the combustion chamber bottom, or on aerodynamic internals, for example, a swirling device for the combustion air.
The baffle plate may preferably be made of high-alloy steel, of ceramic or of ceramic-coated steel.
These and other advantages and features of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention when viewed in conjunction with the accompanying drawings.